linux-kernel - Re: [PATCH] fpga: dfl-afu-region: Add overflow checks for region size and offset

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Date:   Sun, 9 Apr 2023 21:00:24 +0200
From:   Salvatore Bonaccorso <carnil@...ian.org>
To:     Xu Yilun <yilun.xu@...el.com>, Sangsup Lee <k1rh4.lee@...il.com>
Cc:     k1rh4.lee@...il.com, Wu Hao <hao.wu@...el.com>,
        Tom Rix <trix@...hat.com>, Moritz Fischer <mdf@...nel.org>,
        linux-fpga@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fpga: dfl-afu-region: Add overflow checks for region
 size and offset

Hi,

On Fri, Feb 10, 2023 at 04:21:37PM +0800, Xu Yilun wrote:
> On 2023-02-05 at 21:43:26 -0800, k1rh4.lee@...il.com wrote:
> > From: Sangsup Lee <k1rh4.lee@...il.com>
> > 
> > The size + offset is able to be integer overflow value and it lead to mis-allocate region.
> 
> But I didn't see the memory allocation.
> 
> > 
> > Signed-off-by: Sangsup Lee <k1rh4.lee@...il.com>
> > ---
> >  drivers/fpga/dfl-afu-region.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/fpga/dfl-afu-region.c b/drivers/fpga/dfl-afu-region.c
> > index 2e7b41629406..82b530111601 100644
> > --- a/drivers/fpga/dfl-afu-region.c
> > +++ b/drivers/fpga/dfl-afu-region.c
> > @@ -151,12 +151,17 @@ int afu_mmio_region_get_by_offset(struct dfl_feature_platform_data *pdata,
> >  	struct dfl_afu_mmio_region *region;
> >  	struct dfl_afu *afu;
> >  	int ret = 0;
> > +	u64 region_size = 0;
> 
> Reverse Xmax tree please.
> 
> >  
> >  	mutex_lock(&pdata->lock);
> > +	if (check_add_overflow(offset, size, &region_size)) {
> 
> I'm not sure if the check is necessary.
> 
> The offset comes from: offset = vma->vm_pgoff << PAGE_SHIFT
> The size comes from: size = vma->vm_end - vma->vm_start
> Is it possible the upper mm layer passes invalid vma?
> 
> Thanks,
> Yilun

Did you saw the comments on your patch by Yilun? Did it felt trough
the cracks?

Regards,
Salvatore